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Dose-response relationship of ethylnitrosourea-and methylnitrosourea-induced mutations in Drosophila
264 3 Ayaki, T., and I. Yoshikawa, Nagasaki University School o f Medicine, Nagasaki 852 (Japan)
Dose-response relationship of ethylnitrosoureaand methylnitrosourea-induced mutations in Drosophila Induction of recessive lethal mutations by ethylnitrosourea ( E N U ) and methylnitrosourea (MNU) was studied for the X-chromosomes of spermatozoa, mature oocytes and oogonia. These chemicals were fed with sucrose solution for 24 h, at the concentration of 0.02-1.0 mM, to Canton-S males and to heterozygous females derived from a cross of Canton-S males and 0-1 females. The absorption of chemicals ingested by the flies was estimated indirectly by monitoring intake 3H activity from 3H-labeled sucrose added to chemical solutions. The absorption decreased as the concentration of chemical in the sucrose solution increased. The amounts of chemicals absorbed per unit body weight of fly were not significantly different between the sexes, both for ENU and MNU. Mutation yield vs. amount-absorbed curves were clearly linear for all the data obtained from ENU treatment, and for oogonia from M N U treatment, whereas those for spermatozoa and mature oocytes treated by MNU were linear in lower doses and showed a downward curvature in higher doses. The last observation suggests an effect of the higher cell toxicity of MNU. The susceptibility of Drosophila germ cells to the mutation was in the order spermatozoa > mature oocytes > oogonia for ENU, and spermatozoa> mature oocytes= oogonia for MNU. ENU was more mutagenic than MNU in these experiments.
4 Chen Deqing (High-Background Radiation Research Group, China), Laboratory for Industrial Hygiene, China National Centre for Preventive Medicine, No. 2 Xinkang Street, Deshengmenwai, Beijing (People's Republic of China) Cytogenetic investigation on population residing in high-background radiation area of Yangjiang, China
The surface soil of high-background radiation (HB) area in Yangjiang county contains a great deal of fine particles of monazite, which elevate local background radiation level to 330 m R / a , that is about 3 times higher than that in the control area (114 m R / a ) . Blood samples were collected from 122 and 99 middle-school pupils of 15-16 years of age in the HB and control areas respectively for analysing chromosome aberrations. All the people analysed were born and had lived ever since in the respective areas, and had never been exposed to medical radiation. The results showed that the frequency of chromosome aberrations in the HB group was 0.47/100 cells, which was significantly higher than that in the control group, 0.33/100 cells. G-banding technique was also used for analysing some of the above subjects, 34 from the HB area and 40 from the control area. In the HB group 55 aberrations were found in 1771 banded metaphases with a frequency of 3.21/100 cells, while in the control group only 39 aberrations were observed in 2006 metaphases, showing a frequency of 1.94/100 cells. In additiolJ, 13425 children below 12 years of age in the HB area and 13087 in the control area were clinically examined. 14 cases with Down's syndrome (0.104%) occurred in the HB area and 4 cases (0.031%) in the control area, and the difference was statistically significant. In the HB area, the average age of the mothers who gave birth to the children with Down's syndrome was 39.4 years at the births, 50% of them having been older than 40. It seems that maternal age is an important factor affecting the incidence of Down's syndrome, but further investigation is necessary.
5 Ebata, J., K. Ishida and H. Morita, Faculty of the Science of Living, Osaka City University, Osaka 558 (Japan) Effect of cooking conditions on mutagen formation in fried pork Each side of lean pork patties (1 cm thick, about 100 g) was fried on an electric aluminum griddle, initially preheated at the stated temper-
Dose-response relationship of ethylnitrosoureaand methylnitrosourea-induced mutations in Drosophila Induction of recessive lethal mutations by ethylnitrosourea ( E N U ) and methylnitrosourea (MNU) was studied for the X-chromosomes of spermatozoa, mature oocytes and oogonia. These chemicals were fed with sucrose solution for 24 h, at the concentration of 0.02-1.0 mM, to Canton-S males and to heterozygous females derived from a cross of Canton-S males and 0-1 females. The absorption of chemicals ingested by the flies was estimated indirectly by monitoring intake 3H activity from 3H-labeled sucrose added to chemical solutions. The absorption decreased as the concentration of chemical in the sucrose solution increased. The amounts of chemicals absorbed per unit body weight of fly were not significantly different between the sexes, both for ENU and MNU. Mutation yield vs. amount-absorbed curves were clearly linear for all the data obtained from ENU treatment, and for oogonia from M N U treatment, whereas those for spermatozoa and mature oocytes treated by MNU were linear in lower doses and showed a downward curvature in higher doses. The last observation suggests an effect of the higher cell toxicity of MNU. The susceptibility of Drosophila germ cells to the mutation was in the order spermatozoa > mature oocytes > oogonia for ENU, and spermatozoa> mature oocytes= oogonia for MNU. ENU was more mutagenic than MNU in these experiments.
4 Chen Deqing (High-Background Radiation Research Group, China), Laboratory for Industrial Hygiene, China National Centre for Preventive Medicine, No. 2 Xinkang Street, Deshengmenwai, Beijing (People's Republic of China) Cytogenetic investigation on population residing in high-background radiation area of Yangjiang, China
The surface soil of high-background radiation (HB) area in Yangjiang county contains a great deal of fine particles of monazite, which elevate local background radiation level to 330 m R / a , that is about 3 times higher than that in the control area (114 m R / a ) . Blood samples were collected from 122 and 99 middle-school pupils of 15-16 years of age in the HB and control areas respectively for analysing chromosome aberrations. All the people analysed were born and had lived ever since in the respective areas, and had never been exposed to medical radiation. The results showed that the frequency of chromosome aberrations in the HB group was 0.47/100 cells, which was significantly higher than that in the control group, 0.33/100 cells. G-banding technique was also used for analysing some of the above subjects, 34 from the HB area and 40 from the control area. In the HB group 55 aberrations were found in 1771 banded metaphases with a frequency of 3.21/100 cells, while in the control group only 39 aberrations were observed in 2006 metaphases, showing a frequency of 1.94/100 cells. In additiolJ, 13425 children below 12 years of age in the HB area and 13087 in the control area were clinically examined. 14 cases with Down's syndrome (0.104%) occurred in the HB area and 4 cases (0.031%) in the control area, and the difference was statistically significant. In the HB area, the average age of the mothers who gave birth to the children with Down's syndrome was 39.4 years at the births, 50% of them having been older than 40. It seems that maternal age is an important factor affecting the incidence of Down's syndrome, but further investigation is necessary.
5 Ebata, J., K. Ishida and H. Morita, Faculty of the Science of Living, Osaka City University, Osaka 558 (Japan) Effect of cooking conditions on mutagen formation in fried pork Each side of lean pork patties (1 cm thick, about 100 g) was fried on an electric aluminum griddle, initially preheated at the stated temper-